Object Functions and Words Reexamined: Toddlers' Recognition of Function Depends on Object Type.

The role of function in toddlers' object labeling has been debated for decades in developmental science. We aimed to clarify the relation between toddlers' understanding of functions and words using a set of everyday objects that varied in the number of associated functions (e.g., balls can be bounced, thrown, or rolled while toothbrushes primarily brush teeth). Forty 23- to 25-month-old monolingual English-learning toddlers completed a preferential looking paradigm in which objects were used in conventional and unconventional ways, designed to measure expectations about object functional expectations. We also measured toddlers' lexical knowledge about these objects using a looking-while-listening task. Finally, we assessed productive vocabulary size using the MacArthur-Bates Communicative Development Inventory: Words and Sentences. The results suggest that toddlers have expectations about the functions of some objects, but not others. In particular, these expectations were stronger for objects that are tightly linked with their functions in everyday experiences, and for children who have larger vocabularies. These findings also suggest that toddlers' ability to demonstrate functional knowledge may depend on the specific objects included in the task.